Removal of photographically active ingredients from gelatin



Patented Sept. 28, 1948 VA OF PIEIQZI GE H AL XA V INGREDIENTS FRQMGELATIN B'Iitdolph fiain'sch'roder and Marie E. Kahl l" manjRochester;N. Y.,assigi 1tii"s to Eastman nouak Coinfiany;=Roches'ter, N: Y.,ambit-pom: tion'ofNeW'Jersey. No Drawing. Amnioationsegteiiiuer i4;1946; Serial No. 697,156

This "invention relates to'tli' remo'val'of DhOtO- graphically activeingredients front gelatin" or other proteins by treating the gelatifi'or other proteins with certain metals in finely divided form.

Photographic en nilsio'ns' are ordinarily prepared by incorporating aphoto-sensitive silver saltin-gelatinin aqueous solution as theprotective coatin for the photosensitive Silver Salt. A's gelatin is amaterial which is obtained-from natural sources, there is oftentimesoonsieerame variation in the pro ertiesor that material when usedphotographically-.-' For instance, some types of" gelatin have therein91- considerable proportion-of'photogiaphically active ingredients;Because of this-variation it has-heretofore been diflicu-lt to'preparphot ogra hio emulsion or uniform properties following a'setfor'mula'for their preparatiom One object of our invention is toprovide a method for treating gelatin or other proteins whereby aconsiderable proportion of'the photographically active ingredientsthereof are re moved or renderedinactiv'e: Another object of ourinvention is tdprovide" a method for new iii'g'gel-atin or otherproteins with metals infinely divided condition: Other objects of our'inventio'nliwill appear herein. 7

We" have found that" the photographically act'rveing'redients of'gelati'n or other proteins are 2 either removed "oirender'ed inactive bytreating the gelatin or otherpr'oteinswith active metals whose sulfidesare insoluble a'ncl'which will not adversely ali'e'ct' the photographicemulsion which is formed therefrom. Our process in its broadestaspectscomprises-treatin the protein either in aqueous or non-aqueoussolution in liquid form with one of the metals under the designationgiven, in finely divided condition and thereafter subjecting thesolution to filtration to remove the metal particles therefrom. As it isdesirable that the gelatin be in liquid form, ordinarily the operationWill be carried out at a temperature within the range of 30-75 C.Ordinarily, the most convenient procedure is to dissolve the protein inan inert solvent and contact the metal particles therewith. Where theprotein is water-soluble as in the case oi gelatin, albumin, etc., theuse of an aqueous dissolving liquid is desirable. If desired, however,non-aqueous solvents may be used; for instance, gelatin may be dissolvedin formamide and treated with the finely divided metal.

Gelatins and other proteins vary among themselves as to the degree ofphotographic activity which is present therein; Accordingly}- someproteins will nee'd tb be treated for Monger time and with a greateramount of metal per iiiiit weight of protein than-will other roteaseving lesspho'tog'raphic activity. However, even with the gelatins orotherproteihs having a highd gree of photographic activity; the use ofinetil inanarnount' which will not render the photographically activeingredients entirely inactive vvfl lat least reduce the photographicactivity or the gelatin, if only aparti'al reduction inactivity isdesired. Unless, however, only partial reductioh inactivity is'desired,it is ordinarily oesirable to use a large excess-ofmetal so that everyportion of the gelatin or other prbtein'is contacted'with the metalparticles.-

Our invention'is' adapted to the treatment of various types of' gelatin;7 For instance, hydroly'ze'd .gelatin's may be treated in accordancewith our invention to inactivate onotog'rapm c'a'lly active materialstherein as Well as gclatin's which have not been subjectedtohydrolysisan'd which nave-not been subjecte'd to any degradingtreatment. We have found that the treatment iii-accordance with ourinvent on works e ual y well ongela'tin made'froin different raw stocks,such'as' green, salted calfskin, acidulated bone, or dried hide stock.Our invention is also adapt ed to the treatment of proteins generally,if desirable, to inactivate the 'photographically"active materials whichare present therein; For instance, casein," zein, albimnen, soy beanprotein or the like may be treated With'afinely divided metal inaccordance with our'inv'ention, I v

we have also round that the process wortsvery weli'withihquite'a'reason'able range of on: or ifistaeee; entities with" pH values"within the range of 4 to 9 have been deactivated in accordance with ourprocess, and there has been but little variation in the resultsobtained. We have found that there is no necessity for adjusting the pHto any particular value in the carrying out of our process. If the metalwhich is employed is susceptible to the action of acid, it is preferableto treat therewith only those proteins having a pH of above 6.

The metals which are employed to treat gelatin in accordance with ourinvention should be in a condition in which a large amount of surface isexposed which is ordinarily in a finely divided condition. If theprocess is operated by incorporating the finely divided metal into thegelatin solution, it is ordinarily desirable to obtain the best resultsthat the particle size of the metal be at least 150-mesh or smalleralthough in some cases a larger particle size may be desirable.

The materials which are suitable for use in our process are those, thesulfides of which, are insoluble in. water and which will not adverselyaffect a photographic emulsion. The metals which are not suitable arethose the sulfides of which are soluble in water or which hydrolyzerapidly in water solution or which have a derogatory effect uponphotographic emulsions. Some of the metals which in finely divided formare adapted for use in our process are platinum, nickel, cobalt,cadmium, and silver. One of the finely divided metals which we havefound to be particularly suitable in processes in accordance with ourinvention is Raney nickel which is a well-recognized catalytic material.Another finely divided material which is useful is Adams catalyst, whichis finely divided platinum prepared by reducing platinum oxide, also awellknown catalytic material.

The following examples illustrate our invention:

Example 1.--1 g. of Raney nickel were stirred into a 12% aqueous gelatinsolution made up using 1 pound of dry gelatin. The stirring wascontinued for hour at 40 C. The solid materials were then removed fromthe gelatin by filtering through a Kiefer press. The resulting solutionwas chilled, dried down, and was found to be useful for photographicemulsions, and the photographically active ingredients of that gelatinhad been rendered inactive or removed as indicated by the loss indeveloped silver density of the emulsion made with the treated gelatinas compared to that of the untreated gelatin.

Example 2.The procedure of Example 1 was repeated with each of thefollowing metals in finely divided form: cobalt, platinum, lead andordinary nickel. The gelatin which was obtained in each case was foundto be useful for photographic emulsions and the photographically activeingredients thereof had been inactivated.

It appears that in the process in accordance with our invention there isa chemical combination which takes place between the metal particles andthe photographically active materials, and after the treatment of theprotein, the metal particles and any reaction product formed therefromare removed from the mass.

We claim:

1. A method of treating a protein having inherent photographicallyactive ingredients therein to render those photographically activeingredients inactive which comprises treating the protein while insolution with a finely divided metal selected from the group consistingof platinum,

nickel, cobalt, lead, cadmium, and silver, followed by removing themetal particles and any reaction products thereof from the protein.

2. A method of treating gelatin having inherent photographically activeingredients therein to render those photographically active ingredientsinactive which comprises treating the gelatin while in solution with afinely divided metal selected from the group consisting of platinum,nickel, cobalt, lead, cadmium, and silver, followed by removing themetal particles and any reaction products thereof from the proteinsolution.

3. A method of treating gelatin having inherent photographically activeingredients therein to render those photographically active ingredientsinactive which comprises treating an aqueous solution of the gelatinwith a finely divided metal selected from the group consisting ofplatinum, nickel, cobalt, lead, cadmium, and silver, followed byremoving the metal particles and any reaction products thereof from thegelatin solution.

4. A method of treating gelatin having inherent photographically activeingredients therein to render those ingredients inactive which comprisestreating a solution of gelatin having a pH within the range of 4-9 witha finely divided metal selected from the group consisting of platinum,nickel, cobalt, lead, cadmium, and silver, followed by removing themetal particles and any reaction products thereof from the gelatin.

5. A method of treating gelatin having inherent photographically activeingredients therein to render those ingredients inactive, whichcomprises treating an aqueous solution of the gelatin with finelydivided Raney nickel, followed by removing the Raney nickel and anyreaction prod ucts thereof from the gelatin by filtering.

6. A. method of treating gelatin having inherent photographically activeingredients therein to render those ingredients inactive, whichcomprises treating an aqueous solution of the gelatin with finelydivided platinum, followed by remov ing the platinum and any reactionproducts thereof from the gelatin solution by filtering.

'7. A method of treating gelatin having inher ent photographicallyactive ingredients therein to render those ingredients inactive, whichcomprises dissolving the gelatin in water, treating the gelatin for atime with finely divided Raney nickel, and then separating the Raneynickel and any reaction products thereof from the gelatin.

RUDOLPH E. DAMSCHRODER. MARIE E. KAUFFMAN.

(No references cited.)

